The house we are buying in San Antonio has a foundation that is 4 inches higher in the back of the house than the front of the house. No cracks to be found.
Consequently the back yard has a pool that is higher on the side closest to the house. Between the house and pool is a thick slab from the house to the pool.

I suspect the 50 year-old pool has been leaking for years causing the rise in both the house or pool. Just my inexperienced guess. We will need to hire the right sort of inspector of soil engineer - I suppose.

Can anyone provide insight to this sort of problem or advise as to what type of inspection would be best?

If the foundation really has a 4" slope in it (and who determined that figure, and exactly how?), are you prepared to live with that? I suspect furniture placement could be problematic, or at least require a lot of shim material.

Bridgeman; I think having the soil looked at is the best place to start. A few years ago we built a house on the flats near the river and when drainage was put around the house the posts holding up the front porch had no drainage around them. As the soil dryed out the house went down 4" and posts did not move.

This house was built in 1954. The same time Disneyland was being built! I sure hope that whatever this is - it will be fixable. Thanks to all of you. I will be better prepared to get the right professional to help figure this out and know a little more about what to ask.